Separation and filtration products, for instance crankcase filtration assemblies are widely known and used in a number of practical engine applications, particularly with respect to engine oil filtration. For example, during the combustion process in a spark ignited or compression ignition engine, compression gases and other byproducts of combustion may enter into an engine's crankcase. This condition is called blow-by. At this time, gas pressure develops in the crankcase that is above atmospheric pressure. Due to the pressure increase, the gases are ventilated from the engine crankcase through openings, which are usually located in a valve cover assembly or upper engine block area. During this process, the gases in the crankcase typically come into contact with the oil splash lubrication of the crankshaft, as well as other oil saturated components and condensates. These gases become entrained with oil mist while being ventilated from the engine. The oil mist also contains droplets formed by cooling and condensation of hydrocarbons in the gases of the blow-by fluids. The blow-by fluids which contain the gases and condensates are ventilated by the engine crankcase.
When the crankcase ventilates into the surrounding environment it is known as open crankcase ventilation (OCV). In some applications, the gases are returned to the engine through an air intake system and then burned. This is called closed crankcase ventilation (CCV). In CCV, however, there is potential for oil residue to contaminate the turbocharger/air intake system causing necessary repairs, as the oil mist contains oil droplets, including a large fraction that are sub-micron in size or invisible to the naked eye. Such “invisible” droplets for example may be approximately 40 μm or less. Over time, the blow-by flow rate increases. This results in blow-by gases that may be carrying an increased amount of oil mist and other condensate material.
Effective crankcase ventilation filtration helps to maintain a clean engine compartment, protects the environment, and for CCV protects the engine itself. Crankcase ventilation filtration aims to reduce or eliminate the oil droplets, mist, and condensate from the ventilated gases. Crankcase filtration assemblies are often used to remove the oil drops and oil mist (aerosol) from the ventilated gases and air before they enter the surrounding environment (OCV) or before they return to the engine (CCV).
In general, crankcase ventilation filtration typically occurs through a process known as separation, for example through a coalescer element and/or impactor element. Generally, oil droplets and/or mist and water droplets and/or mist, and other condensates are separated from the blow-by gases. When a coalescer element is employed, the smaller particles coalesce into larger drops until they are large enough to be effected by gravity and drain back into the engine crankcase. To aid in the coalescing process, crankcase filtration assemblies often employ a media structure that temporarily collects the small droplets, so that they may form into larger drops that eventually drain from the crankcase filtration assembly. In the example of an impactor element, a structure is employed that gets in the way of, or impacts the contaminated air flow to trap the oil mist. While such structures are helpful to engine oil filtration, oil droplets/mist/other condensate material flowing through the crankcase filtration assembly may, in some situations, exhibit characteristics detrimental to the operating life of the engine oil, such as elevated oil acidity or high viscosity. Improvements can still be made to crankcase filtration assemblies and their structure.